Magnetron question

On Tue, 12 Feb 2019 15:05:11 -0800 (PST), jurb6006@gmail.com wrote:

Well, you didn't mention WHAT country so...

I can tell you this. There are only a few types of magnetrons used in uWave ovens. If the mounting fits, 80%+ chance it works. The actual power is determined by the value of the cap and somewhat by the secondary of the transformer.

They can use a higher rated magnetron in a lower powered oven and they still save money by buying more of the same part. They save money on the transformer or the cap.

The mount has to REALLY match. Close is not good enough.

So the reason microwave ovens cycle on and off at the lower power
settings is because different caps would be needed for different power
outputs? I always thought it was the tube itself, that it worked best
at some certain power output.
Eric

 

[Mike]

On 2/13/2019 10:43 AM, technowb wrote:

Mr. Wieck don't you think this one falls into "hideously expensive to replace"?
Given that a luxury microwave oven costs around 300€ and this one costs more than 700, I'd say it does.. there are almost no more expensive combi ovens in the market: other cheaper ovens I owned lasted 15 years and such.

I would be happy to buy another one and avoid complications, but I cannot afford it, and I am trying to understand the implications of the choice to self-repair it.
I know that there may be serious injuries ahead, that's why I am gathering informations here and there before taking any further step..
Thank you

I haven't heard a convincing argument that the magnetron is the problem.
How did you verify that?

 

On Wednesday, 13 February 2019 20:07:20 UTC, et...@whidbey.com wrote:

On Tue, 12 Feb 2019 15:05:11 -0800 (PST), jurb6006@gmail.com wrote:

Well, you didn't mention WHAT country so...

I can tell you this. There are only a few types of magnetrons used in uWave ovens. If the mounting fits, 80%+ chance it works. The actual power is determined by the value of the cap and somewhat by the secondary of the transformer.

They can use a higher rated magnetron in a lower powered oven and they still save money by buying more of the same part. They save money on the transformer or the cap.

The mount has to REALLY match. Close is not good enough.
So the reason microwave ovens cycle on and off at the lower power
settings is because different caps would be needed for different power
outputs? I always thought it was the tube itself, that it worked best
at some certain power output.
Eric

Early 2 power level nukes used a capacitor & HV switch to reduce anode i. It's cheaper & more reliable to switch the power on & off. And safer. The only time it matters is with mousse.


NT

 

On Wed, 13 Feb 2019 13:43:17 -0800 (PST), tabbypurr@gmail.com wrote:

On Wednesday, 13 February 2019 20:07:20 UTC, et...@whidbey.com wrote:
On Tue, 12 Feb 2019 15:05:11 -0800 (PST), jurb6006@gmail.com wrote:

Well, you didn't mention WHAT country so...

I can tell you this. There are only a few types of magnetrons used in uWave ovens. If the mounting fits, 80%+ chance it works. The actual power is determined by the value of the cap and somewhat by the secondary of the transformer.

They can use a higher rated magnetron in a lower powered oven and they still save money by buying more of the same part. They save money on the transformer or the cap.

The mount has to REALLY match. Close is not good enough.
So the reason microwave ovens cycle on and off at the lower power
settings is because different caps would be needed for different power
outputs? I always thought it was the tube itself, that it worked best
at some certain power output.
Eric

Early 2 power level nukes used a capacitor & HV switch to reduce anode i. It's cheaper & more reliable to switch the power on & off. And safer. The only time it matters is with mousse.


NT

Darn it! I was gonna try to make some mousse tonight in the microwave.
Eric

 

[technowb]

@Mike I have no hard evidence about the magnetron being faulty, however this was the diagnosis made by the tech guy who came over to fix it.
The whirlpool oven displays error F05 (which I was not able to find anywhere in my research over the internet). It displays it only when using features that relay on microwawes, other than that it works fine.
The "official repair guide" - which I have not seen - seems to state that to fix error F05 it is needed to replace the inverter board and the magnetron.
Since the tech guy had a spare new inverter board, he switched it and left it in the oven, unfortunately that didn't fix the error. That's the reason why I am assuming it's the faulty magnetron.. I am actually hoping that, trusting that the tech guy placed a working inverter board inside my oven.

Thank you for your inputs, you're being really helpful

 

[Sjouke Burry]

On 13-2-2019 20:02, John-Del wrote:

On Wednesday, February 13, 2019 at 1:43:38 PM UTC-5, technowb wrote:
Mr. Wieck don't you think this one falls into "hideously expensive to replace"?
Given that a luxury microwave oven costs around 300€ and this one costs more than 700, I'd say it does.. there are almost no more expensive combi ovens in the market: other cheaper ovens I owned lasted 15 years and such.

I would be happy to buy another one and avoid complications, but I cannot afford it, and I am trying to understand the implications of the choice to self-repair it.
I know that there may be serious injuries ahead, that's why I am gathering informations here and there before taking any further step..
Thank you

Apparently (or should I say supposedly), this magnetron replaces the one in your unit:

https://www.directrepair.eu/microwave-oven-2m236m42-00268142-panasonic.html

About 100E with freight. Are you sure the magnetron is bad? A lot of things can prevent it from being powered up: door interlock switch, control board problem, burned relay (or connection - not uncommon on Whirlpools), HV diode or HV capacitor.

Shop for a second hand one of the same age/power range, and swap components.

 

[Ralph Mowery]

In article <5c64a3f5$0$31762$e4fe514c@textnews.kpn.nl>,
burrynulnulfour@ppllaanneett.nnll says...

Shop for a second hand one of the same age/power range, and swap components.

Sometimes that is the only way to repair items. I do not like built in
items for that reason. Or even fancey (expensive) items to do simple
tasks. I really hate the cars that give you almost no options as to what
you want. Last car had to have leather seats if I wanted a V6 engine.
I hate the leather. Makes me sweat in the summer and cold in the winter
before the heated seats warm up. Had the 'moon roof' no need at all
for that as far as I am concerned.

About 10 years ago I bought a house and the only reasonable place for
the refrigerator is a small opening. That ment I was limiated in the
height and especially the width of a unit I could use unless
modifications to the cabinet were made.

 

>"IE: Instead of heating something for the typical one
minute at full power, heating it for two minutes at
half power(or even medium high or 60% if such
setting available)? That way the magnetron cycles
on and off instead of running constantly, and also
the food is more evenly heated. "

No. It is doing the same work AND being thermally cycled. Now had you an older one where they put more than six bucks into it, they had a lower tap on the transformer for the lower power setting. One of those maybe. With that, lower power might just make the tube last longer. Not by cycling on and off for a longer time.

 

>"I suspect magnetrons are the same way. "

It seems CRTs are. I had a Zenith 20" come in, had the best picture I ever saw on that model because the tube was strong. I mean STRONG. Te complaint was there was a slight noise when it was turned off. I discovered that it really wasn't turning off, when the micro said power off it muted the audio and video but the HV, and of course the filament of the CRT and all that was still on. I told them not to fix it. Management didn't agree so it got fixed.

We knew for a long time about CRTs, like NEC bigscreens had active all the time AKB and when you first turned them on they were actually "cathode stripping". Sony's AKB had a delay until beam current was normalized, as told by the AKB circuit. Didn't help, their CRTs were junk by then. But I got this 35 year old Sony in my room with about the best god damn picture you ever saw, and it is never shut off. To shut it up I just switch to a dead source. You will NOT see color like on this thing.

Anyway, the magnetron has a filament so when it cycles on and off the filament thermally cycles and in almost ANYTHING in the physical world thermal cycling is bad.

The old microwaves with the tap, the filament voltage was still the same.

Actually if you look at the power level switch on one of them you can see it is made to switch a few thousand volts. It is not a simple slide switch.

 

For my GE micro, power level cycling is as follows:

HI/Full - Magnetron on continuously
90% - On 27sec, off 3sec
80% - On 24sec, off 6sec. etc etc.
50%/Medium - On 15sec, off 15sec
20%/Lowish - On 6sec, off 24sec

And so on.

I'm sure the designers took everything into
account when providing for all those power
levels. I almost never use Full, except for
when boiling water.

 

[Fox's Mercantile]

On 2/13/19 6:20 PM, jurb6006@gmail.com wrote:

But I got this 35 year old Sony in my room with about the
best god damn picture you ever saw, and it is never shut
off.

Which of course, is entirely relevant to magnetrons.


--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com

 

[Mike]

On 2/13/2019 2:20 PM, etpm@whidbey.com wrote:

On Wed, 13 Feb 2019 13:43:17 -0800 (PST), tabbypurr@gmail.com wrote:

On Wednesday, 13 February 2019 20:07:20 UTC, et...@whidbey.com wrote:
On Tue, 12 Feb 2019 15:05:11 -0800 (PST), jurb6006@gmail.com wrote:

Well, you didn't mention WHAT country so...

I can tell you this. There are only a few types of magnetrons used in uWave ovens. If the mounting fits, 80%+ chance it works. The actual power is determined by the value of the cap and somewhat by the secondary of the transformer.

They can use a higher rated magnetron in a lower powered oven and they still save money by buying more of the same part. They save money on the transformer or the cap.

The mount has to REALLY match. Close is not good enough.
So the reason microwave ovens cycle on and off at the lower power
settings is because different caps would be needed for different power
outputs? I always thought it was the tube itself, that it worked best
at some certain power output.
Eric

Early 2 power level nukes used a capacitor & HV switch to reduce anode i. It's cheaper & more reliable to switch the power on & off. And safer. The only time it matters is with mousse.

Try cooking an egg to dispel that thought.
Older microwaves had minimum on-time because of the filament warm up
time...and the lack of high voltage power supply electronics back then.
A 10-second on-time is plenty of time for localized heating to cause
food to explode.
The newer inverter microwaves have much shorter on-times so food doesn't
explode as easily even at the same average power.

NT
Darn it! I was gonna try to make some mousse tonight in the microwave.
Eric

Under what conditions did the microwave fail?

Did it quit while in use? Between uses?
Any power outages or lightning storms in between?

I've never fixed a newer microwave. All my repairs were diode
replacements in older machines. I don't think I'd even try
to fix my Panasonic inverter without a full set of schematics.
Even then, all the sensors would be a nightmare to reverse-engineer.

I'm gonna make some guesses.
I doubt that the magnetron has failed.
Sure, it can crack if you overheatd it by running it
for long periods nearly empty.

More likely something else failed.
There's not much to cause instant failure of a magnetron
if you didn't overheat it.
I doubt that there are any high voltage components on
the controller that was replaced.
The oven is full of sensors for safety and cook control.
Any of them can cause the system to inhibit the microwave function.
I'd guess that the only things a controller would monitor
might be power supply voltage and temperature.
Just not worth the expense to do more. But there's plenty
more to go wrong.

Here's some reading material.

https://www.thermex-thermatron.com/wp-content/uploads/2015/11/FailureOfMagnetrons_v3.pdf

https://www.repairfaq.org/sam/micfaq.htm

 

[technowb]

Thank you! I've read everything, and I searched for the exact magnetron; unfortunately I have to go for an "80% compatibile model" since everytime I find a website listing the correct model it's either out of stock or the website fails under a 404 error.

I have one more question, since I noticed a difference between apparently the same model by different manufacturers:

Does the shape of the hole of the "microwaves cannon" make some difference? I can't find one with the exact shape of my original model (square): the available shapes of the alternatives are circle and triangle.. should I go for one of those randomly or there are better chances of compatibility if I choose one over the other?

Thank you again

 

[Look165]

Try
https://www.cdiscount.com/electromenager/r-magnetron+panasonic+2m236-m42.html#_his_

technowb a Êcrit le 12/02/2019 à 22:41 :

Hi, I have to replace (in a micorwave oven) a Panasonic magnetron 2M236-M62 which is no longer in production and it's difficult to find in my country.
Some spare parts websites list Panasonic 2M236-M42 as an alternative model, but I am unable to find the datasheets to compare values.

Any advice on where to find those datasheets, or a minimum warranty that they are compatible?

Thank you

 

>"Which of course, is entirely relevant to magnetrons. "

I dunno bout that. A magnetron has a cathode heating up with full plate voltage applied which is known to cause damage to CRT cathodes. That's why Sonys with AKB had a turn on delay until the detected tickle current is up to a certain level. It lessens "cathode stripping". Well lessenED, no more CRTs, more useless knowledge.

Think you bad to the bone ? Got moxy, resources n shit ? Wana make some money ?

Build a left handed microwave. Seriously, there is a market and some people really need them and NOBODY makes them. They all go the same way but not everybody's kitchen goes the same way. Just look at your microwave in a mirror and that is what could sell. You would have 100% of the market for maybe a couple of years.

Get your torches, MIG welders, die grinders, the usual implements of destruction and get rich.

I actually looked into it, it is a big pain in the ass. And you only get a couple years because the big boys will start making them as soon as they detect your presence in the market.

Now THAT's irrelevant...but true.

 

Lefthanded microwaves:

I think I've seen a few lefthanded TV sets(CRT era)!

Where the tuning knob, volume, brighness, speaker
are to the left of the picture tube.

 

[technowb]

Hi guys, thank you all.
I can confirm that in AMW842IX - that uses magnetron 2M236-M62 by default - we can use as an alternative magnetron 2M236-M42 by Panasonic. I am not sure if other brands of the same model works the same, however the oven is on duty again, and trying to repair it was worth the effort.

Thank you again